Scientia Iranica
Volume:21 Issue: 3, 2014

A simple, fast and inexpensive method based on dispersive liquid-liquid microextraction (DLLME) and dispersive solid-phase extraction (DSPE) has been developed for preconcentration and spectrophotometric determination of paracetamol (PC) using pH-sensitive hydrogel (HG). In this study we demonstrate a novel microextraction technique, entitled “semi solid-liquid dispersive microextraction” which can be successfully used for preconcentration of analytes of interest from aqueous samples. The procedure involves the oxidation of paracetamol by Fe(III) and a subsequent reaction with ferricyanide in the presence of HCl to yield Prussian Blue (PB) complex. In the extraction step, appropriate amounts of poly(styrene-alt-maleic anhydride), as a pH-sensitive hyrogel, was injected into the aqueous solution, so a cloudy solution was formed. Organic and inorganic compounds having the potential to interact with polymer particles could be extracted into the organic phase. For our case PB complex could be extracted to the cloudy phase. After centrifugating, the hydrogel-rich phase was sedimented at the bottom of centrifuge tube. The absorbance of the sedimented phase diluted in methanol was measured at the absorption maximum of 733 nm (λmax of PB in hydrogel). The absorbance was linear to paracetamol concentration in the range of 0.01-0.5 μg mL-1 with a correlation coefficient of 0.995.

1-Aryl-2,3-dihydro-3-phenyl-1H-naphth[1,2-e][1,3]oxazines are synthesized in good to excellent yields in the presence of LaCl3/ClCH2COOH as an inexpensive and environmentally benign catalytic system under solvent-free conditions.

An ecient and convenient synthesis of benzo[a]xanthene-11-one derivatives has been achieved by a one-pot, three-component reaction of various aromatic aldehydes with 2-naphthol and dimedone in the presence of Silica supported boron tri uoride nanoparticles (BF3-SiO2 NPs) as a mild solid acid catalyst in improved yields.

Novel bipodal, tripodalpiperidin-4-ones and their corresponding piperidin-4-ols were subjected to dielectric analysis which signifies drug delivery. The studies revealed that these compounds can exhibit better drug release in association with polymer.

A room-temperature procedure is developed for the direct synthesis of monoarylidene derivatives of pyran-4-one and piperidin-4-one systems under solvent-free conditions. Relatively high yields of products are obtained from the reaction of ketones 1 with different aromatic and aliphatic aldehydes under the catalytic system of TMSNMe2 and MgBr2·OEt2. Notably, formation of the undesired bis counterparts as a major limitation of these reaction types, is minimized using the employed conditions.

A one-pot, three-component condensation of aldehydes, 2-naphthol and 2- aminobenzothiazole in the presence of multi-SO3H functionalized ionic liquid (synthesized from hexamethylenetetramine and 1,4-butane sulfonate), as an e ective catalyst for the synthesis of 1-(benzothiazolylamino)methyl-2-naphthol derivatives, under thermal and solvent-free conditions, is described. These products involve two biologically active parts; Betti''s base and benzothiazole. The present methodology o ers several advantages, such as good yields, short reaction times, and easy work-up. The catalyst could be recycled and reused without substantial reduction in its catalytic activities.

4-hydroxycoumarin 2a and 4-hydroxy-6-methyl-pyran-2-one 2b were applied in a one-pot reaction with Baylis-Hillman adduct acetates 1 to form novel 3-benzylpyrano [3, 2-c] pyran-2, 5-diones 3 in high yields (70-85%). The synthesized framework isavailable in many biologically active moieties. The reaction was carried out under di erent conditions to achieve optimum conditions. The results indicated that Et3N, as a base under solvent-free conditions, was optimum. The reaction procedure and puri cation method are mild and straightforward.

A simple, efficient and one-pot method has been developed for the synthesis of densely functionalized aryl derivatives of 2-amino-3-cyano-7-hydroxy-4H-chromene by the domino Knoevenagel-Michael-cyclization reactions of aromatic aldehydes, resorcinol and malononitrile in the presence of a catalytic amount of Na2CO3 under grinding conditions.

An easy and highly efficient one-pot, three-component synthesis of rhodanines is reported. The reaction of primary amines, carbon disulfide and chloroacetyl chloride proceeded in the absence of solvent and catalyst, to afford 2-thioxothiazolidin-4-ones in good to excellent yields.

In this work, an experimental study of CO2 hydrate formation kinetics was performed. The effects of the stirring rate and initial pressure on the hydrate formation rate were investigated. The results showed that a stirring rate of 600 rpm was optimum for increasing the CO2hydrate formation rate, especiallyat lower temperatures. The effects of additives on the hydrate formation rate were also investigated. Three surfactants, sodium dodecyl sulfate (SDS), dodecyl trimethyl ammonium bromide (DTAB) and TritonX-100 (TX-100) were tested. DTAB and TX-100 were new surfactants for investigation on CO2 hydrate formation kinetics. SDS and DTAB did not significantly affect the hydrate formation rate at concentrations of 300 and 500 ppm, whereas SDS increased and DTAB insignificantly decreased the hydrate formation rate at 1000 ppm. Furthermore, TX-100 negligibly decreased the hydrate formation rate at 300 and 500 ppm, but significantly decreased the rate at 1000 ppm. In contrast, the application of thermodynamic additives, tetrahydrofuran (THF) and tetra-n-butyl ammonium bromide (TBAB) at low concentrations increased the hydrate formation rate, and these additives affectedthe rate of hydrate formation in a manner similar to kinetic promoters.

In this work, the process of free gravity drainage under the influence of ultrasonic waves was investigated. A glass bead pack porous medium was used to perform the free fall gravity drainage experiments. The tests were performed in presence and absence of ultrasonic waves and the data of recovery were recorded versus time in both conditions. The wetting phases relative permeability curve were obtained using the data of recovery versus time based on the Hagoort backward methodology and afterward, using the wetting phase relative permeability curve, the relative permeability of non-wetting phases were calculated by performing history matching to the experimental production data. The results revealed that ultrasound considerably increases the recovery factor of the free gravity drainage process. It was also observed that the relative permeability of both wetting and non-wetting phases increases under exposure to ultrasonic waves. The results of this work can be helpful to better understanding/evaluating the behavior of relative permeability curves of both wetting and non-wetting phases during free gravity drainage process under the exposure to ultrasonic wave.

Removal of zirconium from its dilute aqueous solution by using Aspergillus niger as dried and living biomass was investigated. Through that, the effect of some operational parameters including pH, temperature, contact time, initial concentration of zirconium, and dose of biomass on biosorption were studied. Based on the results, it was concluded that the uptake of zirconium by both dried and living biomasses is pH dependent, and maximum uptake was observed in pH=3.1 for both biomasses. The maximum uptake capacity of living biomass was obtained in 30 OC. However, the biosorption of zirconium by dried biomass was not affected by temperature. The maximum uptake capacity for living and dried biomasses (78.8 mg/g and 142 mg/g, respectively) was obtained at equilibrium time of 120 min and 30 min, respectively. Equilibrium isotherms showed that adsorption of zirconium by living biomass follows Freundlich model and uptake of dried biomass follows Langmuir model. Kinetic studies showed that both kinds of biomasses follow second order model of kinetic.

In fractured reservoirs, large variation of permeability due to the presence of fractures leads to the changes in production mechanism comparing to the conventional reservoirs. Hence, an appropriate model with ability to describe the reservoir properly can provide a more confident prediction of the future performance of the reservoir. One of the features of a representative model is the number and height of matrix blocks. The determination of these two parameters is one of the decisive steps in the calculation of an accurate amount of oil production from these reservoirs. In fact, matrix height shows its effect as a gravity force, which is one of the driving mechanisms. If the matrix height is less than the threshold height, it will have a significant influence on production. The aim of this study is therefore to obtain mathematical relations that are able to estimate the matrix height from material balance analysis. In this study: (a) The Havlena and Odeh’s straight line form of the material balance equation has been extended to analyze the behavior of naturally fractured reservoirs and (b) Equations that can be used to estimate the matrix height are obtained for the Warren-Root and Kazemi models.

Renewable resources such as natural fillers in reinforced materials with their new range of applications represent an important basis of fulfilling the ecological objective of creating environmental friendly materials. Study on composites using breadfruit seed hull ash particles (BFSHAp) as a reinforcing material and recycled low-density polyethylene (RLDPE) as a novel matrix has been made. The composites were produced by varying the breadfruit seed hull ash particles from 5-25wt% and the properties studied using mechanical tests and microstructural analysis. The results show that there was a uniform distribution of the breadfruit seed hull ash particles in the microstructure of RLDPE composites which is the major factor responsible for the improvement in the mechanical properties.